This is a straight forward explanation for the expression “there’s method in my madness.”
It’s actually from a play by William Shakespeare. In his play Hamlet, written in 1602 in Act 2. Scene 2. The actual line from the play, spoken as an aside by Polonius is:
POLONIUS
Though this be madness, yet there is method
in ‘t. Will you walk out of the air, my lord?
Since then, the line has been modified into the more popular version we use today: “There’s method in my madness.”